Tube-bending tool

ABSTRACT

Disclosed is a tube-bending tool comprising a forming roll adapted to be turned by means of a crank. A tube clamp bar is operatively secured to the forming roll and is provided with a tube clamp. A cam shoe is pivotally mounted on the tool cover and is adapted to be moved into or out of engagement with the forming roll by means of a handle. Opposed grooves are provided in the forming roll and the cam shoe for the purpose of supporting the tube as the forming roll is rotated. The opposed grooves have a transverse dimension slightly larger than the tube outer diameter whereby the tube is free to elastically deform in a transverse plane during the bending operation.

United States Patent [72] lnventors Harry G. Dodge Painesville;

Emery J. Zahuranec, Solon, both of, Ohio [211 App]. No, 775,259 [22] Filed Nov. 13, 1968 [45] Patented June 15, 1971 [73] Assignee Crawford Fitting Company Solon, Ohio [54] TUBE-BENDING TOOL 14 Claims, 15 Drawing Figs.

[52] US. Cl 72/310, 72/154, 72/159, 72/217 [51] Int.Cl B2ld5/04 (50] Field of Search 72/149, 154,159, 217, 298,308, 310, 316, 318, 319, 387, 388, 295, 297, 320, 321, 322; 29/157 A [56] References Cited UNITED STATES PATENTS 3,274,816 9/1966 Held 72/189 Primary Examiner- Richard J. Herbst Assistant ExaminerMichael J. Keenan A!l0rney Fay, Sharpe and Mulholland ABSTRACT: Disclosed is a tube-bending tool comprising a forming roll adapted to be turned by means ofa crank. A tube clamp bar is operatively secured to the forming roll and is provided with a tube clamp. A cam shoe is pivotally mounted on the tool cover and is adapted to be moved into or out of engagement with the forming roll by means ofa handle. Opposed grooves are provided in the forming roll and the cam shoe for the purpose of supporting the tube as the forming roll is rotated. The opposed grooves have a transverse dimension slightly larger than the tube outer diameter whereby the tube is free to elastically deform in a transverse plane during the bending operation.

PATENTEU JUHI 5 I971 SHEET 2 OF 4 I56 l5 4 42 FIG.7

FIG a INVENTO HARRY c. DOD E BYEMERY J.ZA|HURANEC ATTORNEYS.

PATENTEU JUN} 5197! SHEET 3 BF 4 RY Y J 1 dwmgwbw ATTORNEYS.

TUBE-BENDING TOOL BACKGROUND OF THE INVENTION This invention relates to a hand-operated tube-bending tool for the purpose of placing bends in tubing ofcopper, steel, or the like.

Hand-operated tube-bending tools are well known to the art. As an example of such a tool, reference is made to U.S. Pat. No. 3,236,082 to Beck et al. As shown in the Beck et al. patent, a squared crank arm which carries a hand roller at its outer end is nonrotatably received in the recess ofa stub shaft to which is secured a bevel gear. Rotation of the crank arm about the stub shaft axis produces rotation of the bevel gear thereby imparting rotation to a forming roll of the tube bender.

The forming roll itself is formed with an arcuate peripheral groove which terminates at its ends in a .flat section or length. A tube clamp bar extends from the forming roll and is provided with an arcuately shaped tube-clamping jaw. The tube clamp bar also carries a tube stop. A U-frame support member is secured to the tube-bending tool and is provided with a pair of idler tube rollers. A peripheral groove is formed in each of the rollers and is of the same shape and depth as the groove of the forming roll. As illustrated in FIGS. 2 and 3 of Beck et al. U.S. Pat. No. 3,236,082 the tube is fully enclosed within the peripheral complementary grooves of the forming roll and the idler roller 54 at the plane of contact of these members.

As illustrated in FIG. 2 of the Beck et al. U.S. Pat. No. 3,236,082, rotation of the crank 21 imparts rotation to the forming roll 28 and accordingly to thebar member.42. The tube having been secured to the bar 42 is thereupon bent about the axis of the forming roll.

The crank is rotated until the stop means 44 abuts the pointer stop member 38. At this juncture, a bend of predetermined angularity will have been produced in the tube. The spring-loaded plunger 58 is next lifted to free the frame 52 for outward swinging movement of the idler roller 54. After the clamping jaw 43 has been swung free of engagement with the tube, the tube may be withdrawn from the tool.

Several shortcomings have been noted in prior art tubebending tools such as that shown in the Beck et al. U.S. Pat. No. 3,236,082. With particular reference to the Beck et al. patent, FIG. 1, the U-frame member 52 has been found cumbersome to operate particularly where the tool is utilized for repetitive production bending operations. Furthermore, it has been found that prior art tools are not completely successful in eliminating buckling in the tube wall during bending operations. Buckling of the tube wall is particularly a problem when thin wall tubing is bent.

This invention contemplates a tube-bending tool that provides a tube-supporting member in the form ofa cam shoe that may be quickly and effortlessly brought into contact with the tube and the forming roll of the tube-bending tool. This invention further contemplates the provision of particularly defined opposed grooves in the forming roll and the cam shoe to provide support for the tube during the bending operation. The opposed grooves are defined by walls having a cross-sectional dimension slightly larger than the tube outer diameter in order to permit the tube to elastically expand during bending thus to minimize buckling and promote smooth bends.

SUMMARY OF THE INVENTION Briefly summarized, the tube-bending tool of this invention comprises a forming roll including crank means for turning said roll, usually through a suitable gearing arrangement. A tube clamp is operatively secured to the forming roll. A cam shoe cooperates with the forming roll in order to support the tube against the forming roll. Opposed peripheral grooves are defined in the forming roll and the cam shoe, and at the plane of contact of the cam shoe and the forming roll the walls defining the grooves fully enclose the tube. The transverse dimension of the grooves at the plane of contact is slightly larger than the outside diameter of the tube thereby to permit the tube to deform elastically in a transverse plane during the bending operation. The cam shoe itself is provided with handle means to enable the operator to bring the cam shoe quickly into or out of engagement with the tube and the forming roll during the bending operation.

DESCRIPTION OF THE DRAWINGS For a more complete description of the tube-bending tool of this invention, reference is now made to the accompanying.

figures in which:

FIG. 1 is a top plan view of a portion of the tube-bending tool of this invention and showing the position of the forming roll immediately prior to the bending operation;

FIG. 2 is a top plan view of a portion of the tube-bending tool of this invention and showing the position of the forming roll after a bend has been placed in the tube;

FIG. 3 is a top plan view, partially cutaway, of the forming roll of this invention and showing a modification of the forming roll when the tube clamp bar is not utilized;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 1;

FIG. 5 is a top plan view, partially cut away, of the forming roll and cam shoe of this invention with the cam shoe in the locked or closed position;

FIG. 6 is a top plan view of the forming roll and cam shoe of this invention with the cam shoe in the unlocked or open position;

FIG. 7 is an end view, partially in section, taken along the line 77 ofFIG. 1;

FIG. 8 is an end view, partially in section, similar to FIG. 7 and showing the tube clamp in the raised position;

FIG. 9 is a schematic repi'esentation of the geometrical relationship of the peripheral groove in the forming roll and the peripheral groove in the cam shoe;

FIG. 10 is a side elevational view, partially in section, of a portion of the body of the tube-bending tool of this invention;

FIG. 11 is a top plan view taken along the line 11-11 of FIG. 10;

FIG. 12 is a cross-sectional view of the crank arm of the tube-bending tool of this invention; crank FIG. 13 is a cross-sectional view taken along the line 13-13 of FIG. 12;

FIG. 14 is a partial cross-sectional view taken along the line 14-14 of FIG. 2; and

FIG. 15 is a schematic representation of the opposed peripheral grooves of the forming roll and cam shoe of FIG. 14.

DESCRIPTION OF THE INVENTION Reference will first be made to FIG. 10 wherein there is shown in partial section a portion of the body of the tube bending tool of this invention. As shown in FIG. 10, body 12 is comprised of a base 14 and a cover plate 16 which is secured to the base by means of capscrews (not shown) or the like. The base 14 has depending from its bottom, centrally thereof, a block 18 with flat faces 20 to which may be applied the jaws of a vice (not shown) for holding the tool on a bench or more preferably, on a single column to provide space for compound angle bending. The base member 14 and cover plate 16 define a cavity 22 for housing the bevel gears 24 and 26. The gear 24 is fixed to the inner end of a stub shaft or crankshaft 28 by means of a key (not shown) or other suitable means. The shaft 28 is journaled in the sidewall of the base member, its outer end being provided with a hex surface 30 for receiving the free end ofa crank arm 32 (FIG. 2).

Gear 26 is rotatably supported by the stub shaft 34 which has its lower end journaled in the bottom of the base as indicated at 36. The hub of gear 26 is fixed to the shaft 34 by appropriate means such that rotation of the stub shaft 34 will be transmitted to gear 26and vice versa. The hub of gear 26 is journaled in the cover plate 16, as indicated at 38, to provide support for the gear.

Although not shown in FIG. 10, it will be observed from FIG. 7 that the shaft 34 extends above the cover pate 16 and a forming roll 40 is fixed thereon by means of a spline or key (not shown). Reference is also made to FIG. 1 wherein the forming roll 40, stub shaft 34 and cover plate 16 are shown. A washer 42 (FIG. 7) is interposed between the forming roll and cover plate to reduce friction between the forming roll and the cover plate on relative rotation.

The outer end of the stub shaft 34 (FIG. 7) includes a hex surface 44 similar to the hex surface 30 of the stub shaft 28. In the event that it is inconvenient to turn the gear 24 by means of the stub shaft 28, the crank arm 32 may be removed from the stub shaft 28 and positioned on the stub shaft 34 at the hex surface 44 in order to rotate forming roll 40. This provides distinct advantages in performing certain types of bends.

A pair of bosses 46 (FIG. extend from the bottom wall of the base 14 and provide support for a stop plate 48. Fasteners 50 are used to secure such plate to the bosses,

As shown more clearly in FIG. 11, stop plate 48 is generally semicircular in shape and provides a pair of stop surfaces 52. Pin 54 depends from bevel gear 26 and is adapted to contact the stop surfaces 52 as the bevel gear 26 rotates. The plate 48 thus acts as an internal stop to limit rotation of the bevel gears, and consequently the forming roll 40, to a specified arc of travel.

Also provided is an adjustable exterior stop to limit rotation of the forming roll. In this connection, as seen in FIG. I, an abutment plate 56 is nonrotatably secured to stub shaft 34 as by means of a key 58. Abutment plate 56 provides a stop surface 60 which is adapted to contact a pointer 62 after a specified degree of rotation. With particular reference to FIG. 10, it may be seen that the upper edge of the base member 14 and the lower edge of the cover plate 16 are provided with an annular recess or ledges which together define an annular slot 64. A locking bolt and a knurled head 66 (FIG. 1) cooperate to lock the pointer 62 in place at any desired angular position about the periphery of the cover plate. It will be noted from FIG. 1 that the upper surface of cover plate 16 is provided around its circumferential edge with a degree scale 68 to assist the operator in placing a specified bend in the tube. For a further description of the pointer 62 and locking bolt, reference is made to the Beck et al. U.S. Pat. No. 3,236,082.

CRANK Attention is now directed to FIGS. 12 and 13 for a description of the crank mechanism used as an element of the tool of this invention.

As has been previously pointed out, crank arm 32 is adapted to be nonrotatably secured to the stub shaft 28 at the hex surface 30 for purposes of imparting rotary motion to the stub shaft 28, and consequently the forming roll 40, by means of the interengaging bevel gears 24, 26.

As is shown in FIGS. 12 and 13, crank arm 32 comprises a body 70 having a bore 72 and counterbores 74 and 76. Rotatably supported at one end of body 70 is a cylinder 80 having a plurality of teeth 82 on the external surface thereof. Teeth 82 define a plurality of recesses 84 for a purpose to be described more fully hereafter. A passageway extends through the cylinder 80, the walls of said cylinder defining said passageway being generally hex shaped and complementary to the hex shaped external surface 30 of the stub shaft 28. Thus, when stub shaft 28 is received within the passageway of the cylinder 80, the cylinder and stub shaft are secured to one another against relative rotation as is shown in FIG. 13.

Slidably received within the counterbore 76 of body 70 is a cylindrical pin or shaft 86. Pin 86 includes a cylindrical projection 88 slidably disposed in bore 72. A compression spring 90 is disposed about the cylindrical projection 88 so as to abut the and shoulder of pin 86 and the radial wall of body 70 defining the counterbore 76. The purpose of the compression spring 90 is to bias the pin 86 normally in a direction opposite the arrow of FIG. 12.

The end of the cylindrical projection 88 is threaded at 92 for reception in a tapped hole of carrier 94. Pivoted on carrier 94 by means of pin 96 is a pawl 98 having teeth 100 thereon. As shown in FIG. 13, teeth 100 are adapted to be selectively received within recesses 84 of cylinder 80. Pin 96 permits pawl 98 to pivot slightly about the pin axis as the pawl engages cylinder 80.

As is shown in FIG. 12, the cylinder 80, absent interengagement of teeth 100 and recesses 84, is free to rotate within body 70 while being retained against axial displacement by means of snap ring 102 and cover plate 104. Cover plate 104 also permits access to the pawl 98, pin 96, and carrier 94. The cover plate is secured to the body 70 by any suitable fastening means such as screws extending through the cover plate and into the body at 106 (FIG. 13).

Cylindrical pin 86 extends into an end of body 70 (FIG. 12) where the pin abuts a camming piston 108. Camming piston 108 includes a generally cylindrical external surface 110 slidably received within a counterbore 112 of the body. A cylindrical shoulder 114 of lesser diameter than the cylindrical surface 110 is defined at one end of the camming piston. A generally frustoconical camming surface 116 connects shoulder 114 and cylindrical surface 110. Camming piston 108 further includes a bore 118 and a counterbore 120, the latter of which receives a compression spring 122.

A cylindrical connector element 124 is disposed within the bore 118 of the camming piston. Cylindrical connector element 2124 includes a flange or shoulder 126 fixed thereto. Shoulder 126 is adapted to abut an internal radial wall surface of body 70 when an end of the connector element is disposed within a bore 128 of body 70.

A washer 130 is received within a counterbore of body 70. Screw 132 is threadedly received in a tapped hole at one end of the connector element 124 and, in cooperation with the washer 130, permits connector element 124 to rotate with respect to body 70 while disposed in bore 128. Compression spring 122 disposed within counterbore 120 of the camming piston 108 is adapted to abut shoulder 126 and a radial wall of the camming piston 108 defining the counterbore 120. The purpose of compression spring 122 is normally to bias the camming piston to the left of FIG. 12.

Attached to the body 70 by means of the connector element 124 and screw 134 is a handle grip 136. Handle grip 136 comprises a generally cylindrical element 138 including a laterally opening slot or recess 140 which receives a pivotal lever 141. As shown in FIG 12, cylindrical element 138 may include an internal flat portion 142 at the bottom of recess 140 which serves as an anchoring surface for one end of connector element 124. A washer 144 is interposed between the element 138 and the body 70 to reduce friction between the opposed relatively rotatable surfaces of handle grip 136 and crank body 70.

It will be seen from FIG. 12 that handle grip 136 including cylindrical element 138, lever 141 and connector 124 is free to rotate with respect to body 70 about the axis of connector 124. Thus, the operator may grip the element 138 and depress lever 141 while turning the crank. The relative position of lever 141 with respect to the operator's hand will not change during the rotation of the crank.

Pivotal lever 141 has depending therefrom a camming ring 146 having a nose portion 148. Camming ring 146 is generally annular in shape so that the connector 124 may pass through the ring. Thus, as the lever 141 is pivoted about pin 150, the nose portion 148 of ring 146 will abut the camming piston 108. Since during rotation of the crank the lever 141 will rotate with respect to body 70, nose 148 of camming ring 146 may rotate with respect to camming piston 108. While rotating, however, nose 148 may still bear against piston 108.

The operation of the crank arm 32 of FIGS. 12 and 13 will now be briefly described. compression spring 122 normally biases camming piston 108 to the left of FIG. 12 causing lever 141 to assume an outwardly pivoted position with reference to the external surface of cylindrical element 138. Compression spring 90 will normally bias pin 86 in an upward direction of FIG. 12 thus to hold teeth 100 of pawl 98 out of recesses 84. In this position, cylinder 80 is free to rotate or freewheel within the body 70 of the crank arm.

When the operator squeezes lever 141 into the position of FIG. 12, nose 148 of camming ring 146 contacts camming piston 108 causing it to move to the right of FIG. 12. Movement of camming piston 108 to the right produces a downward movement of pin 86 as the frustoconical camming surface 116 moves along the bevelled ti'p portion of pin 86. A downward movement of pin 86 in the arrow direction of FIG. 12 imparts a downward movement to the entire linkage bringing teeth 100 of pawl 98 into recesses 84 of cylinder 80 thereby to lock cylinder 80 against rotation with respect to body 70.

In the position of FIG. 12, therefore, a rotation of handle grip 136 and body 70 about the axis of cylinder 80 will produce rotation of the cylinder 80 inasmuch as the cylinder is locked to the body 70.

Thus, with crank arm 32 connected to stub shaft 28 as shown in FIG. 2 the operator may impart rotary movement to the forming roll 40 as by depressing or squeezing lever 141 and thereafter rotating the crank arm about the axis of stub shaft 28. When the require rotation of the forming roll has been completed, the operator merely releases the lever 141 and the crank arm will freewheel with respect to the stub shaft and assume a downward position with handle grip 136 out of the immediate working area of the operator.

For a more complete description of the crank arm and the operation thereof reference is made to copending application Ser. No. 775,02] assigned to the Crawford Fitting Company.

TUBE CLAMP A description of the tube clamp structure of the tube-bending tool of this invention will now be made with reference to FIGS. 1,7 and 8.

As may be seen in FIG. 1, forming roll 40 is provided with a flat face 152. A tube clamp bar 154 is screw threadedly received in the forming roll 40 at flat face 152.

Pivotally mounted on the tube clamp bar 154 is a tube clamp mechanism 156. As may be seen in FIGS. 7 and 8, tube clamp 156 includes an arm 157 which extends radially from bar 154, curves at 158 and subsequently forms a leg 160. The curved portion 158 of the arm 157 has a slot 162 along its length which permits a handle 164 to be inserted therethrough. In practice, the slot 162 extends through approximately 90 on the curved portion 158 whereby the handle 164 may be pivoted through the same number of degrees. The handle 164 includes a collar 166 and a locking jaw 168. As shown in FIGS. 7 and 8, the cross section of locking jaw 168 is generally V-shaped to provide support for the outer wall of the tube 170 both above and below the axis of such tube.

In operation, the tube clamp mechanism is first located as shown at FIG. 8 while the tube 170 is positioned properly in the tube-bending tool. The tube clamp mechanism 156 is then grasped by the handle 164 and pivoted from the position shown in FIG. 8 to the position of FIG. 7. Once the arm 157 is in the position of FIG. 7, continued pivoting of handle 164 causes locking jaw 168 to rotate circumferentially about the tube 170 while handle 164 moves from the upper end of slot 162 to the lower end thereof into the position of FIG. 7.

To release tube 170, the handle 164 is rotated clockwise and the tube clamp mechanism 156 is thereafter raised into the position of FIG. 8.

For a more complete description of the tube clamp mechanism, reference is made to copending application Ser. No. 622,185 assigned to the Crawford Fitting Company.

In an alternate embodiment of this invention where it is desired to eliminate the tube clamp bar 154 for the performance of certain bends, the tube clamp mechanism 156 is directly pivoted at the forming roll 40 by means of fastener 172 as shown in FIG. 3. Thus, with fastener 172 threadedly secured to forming roll 40 in lieu of tube clamp bar 154, tube clamp mechanism 156 is pivoted directly to forming roll 40 to provide suitable engagement with the tube surface in the manner previously described.

TUBE STOP The tube stop of the tube-bending tool of this invention will now be described with reference to FIG. 1. Tube clamp bar 154 carries an adjustable tube stop 174 comprising a hinged jaw 176 which is adapted to be clamped at any point on the tube clamp bar 154 by means of thumbscrew 178. Extending from the hinged jaw 176 is a tube abutment member 180 which carries a centering tip 182.

Tube stop 174 thus functions to provide support for the end of tube as the centering tip 182 is disposed within the tube end as is shown in FIG. 1. To adapt tube abutment member to various wall thicknesses of available tubing material, several tube abutment members can be employed with varying diameters of centering tip 182.

A suitable scale 184 is provided on the external surface of the tube clamp bar 154 in order to assist the operator in positioning the tube stop on the tube clamp bar.

Within the scope of this invention alternate tube stop structures may be used with the tube-bending tool to provide support for the tube end during the bending operation. The particular tube stop shown in FIG. I is described in greater detail in the Beck et al. US. Pat. No. 3,236,082. For alternate embodiments of tube bender stops and in particular tube bender stops suitable for the placing of compound bends in tubes, reference is made to copending applications Ser. Nos. 583,30l and 775,022 assigned to the Crawford Fitting Company.

CAM SHOE Attention is now directed to the cam shoe of this invention. With particular reference to FIG. 5, cam shoe 186 is pivotally secured to cover plate 16 by means of fastener 188. An elongated slot 190 is defined in cam shoe 186 and includes camming surfaces 192, 194. A tube-receiving groove 200 is defined in cam shoe 186 along an edge adjacent forming roll 40.

More specifically, as shown in FIG. 4, face 198 of cam shoe 186 is generally planar and is interrupted by an arcuate groove 200 defined by walls of the cam shoe. As is more clearly shown in FIG. 15, groove 20 is semicircular in section, the walls defining the groove being defined by a radius R drawn from a point 202 in the plane of face 198. The radius R is selected to be approximately equal to the radius of the tube 170 to be inserted in the tube-bending tool.

Cam means are provided for the cam shoe in order to pivot the shoe about the axis of fastener 188. As is shown in FIG. 5, the particular cam means of this invention comprises a circular cam member 204 eccentrically pivoted with respect to cover plate 16 by means of pin 206. A handle 208 extends from the circular cam member 204 and is adapted to be moved by the operator about the axis of pin 206 thus bringing the circular cam member into engagement with either one of the camming surfaces 192 194. In the: position of handle 208 of FIG. 5, the circular cam member 204 abuts camming surface 192 thus to lock cam shoe 186 in place. Upward movement of handle 208 in FIG. 5 (to the position of FIG. 6) produces pivoting of the circular cam member 204 and subsequent engagement of cam member 204 with camming surface 194 thus to pivot cam shoe 186 to the unlocked position.

In the preferred embodiment of the tube-bending tool of this invention, the elongated slot 190 (as shown in FIGS. 5 and 6) has a slot width exceeding the diameter of cam member 204 Since cam member 204 is eccentrically pivoted, it will swing in an are having a radius of curvature exceeding the radius of the cam member itself. Thus, a swinging action of the handle 208 will bring the circular cam; member 204 into contact with either of the camming surfaces 192, 194 at the option of the operator.

It will also be noted from an examination of FIG. that the point of contact of the cam member 204 and the cam shoe 186 (as shown at point 210) and the center of the pivot pin 206 lie in a line that is parallel to a line drawn between the center 222 of forming roll 40 and the point of tangential contact 212 of the cam shoe and the forming roll. Thus, the circular cam member 204 is in a position of dead enter with the cam shoe 186 abutting the forming roll 40. Coincident with this dead center position, nose 214 of handle 208 abuts the cam shoe 186 so as to prevent further pivoting of the circular cam member in a direction that will tend to unlock the cam shoe.

FORMING ROLL Attention will now be directed to a discussion of the forming roll. As may be seen from FIG. 1, forming roll 40 is generally circular in shape throughout an arc of approximately 270. A first flat face or surface 152 is provided for the purpose of receiving the tube clamp bar 154. A second flat face or surface 216 is also provided on the forming roll for a purpose to be discussed more fully hereafter. A groove 218 is provided about the periphery of the forming roll 40 and extends throughout the second flat face 216 and arcuate face 220 until it intersects the first flat face 152.

Groove 218 in the forming roll 40 is irregularly defined and reference is now made to FIG. 9 for a geometrical schematic representation of the generation of this groove.

Arcuate face 220 of forming roll 40 is defined on a uniform radius V from the center 222 of forming roll 40. Flat face 216 is tangent to face 220, at 212, and is thus defined at the distance V from axis A-A passing through center 222.

The bottom of groove 218, however, does not follow the conformation of flat face 216 and arcuate face 220 exactly in that, broadly speaking, the depth of the groove increases as it progresses clockwise about the periphery of forming roll 40.

To the left (as viewed in FIG. 9) of the tangential point of contact 212 of the cam shoe 186 and the forming roll 40 (with the forming roll and cam shoe in the position of FIG. 1) the groove 218 of the forming roll has a depth D equal in magnitude to the radius R of groove 200 of cam shoe 186, To the right of point 212, the groove increases gradually in depth until it achieves a value D which remains constant thereafter.

The groove 218, unlike groove 200, is not truly semicircular in cross section, having slightly outwardly diverging flat sides 230 joined by a radius R of somewhat smaller magnitude than radius R of groove 200. Thus, the opposed grooves 200, 218 at, and to the left of, point 212 do not together form a perfect circle although the depth of the grooves, in this region, is essentially the same.

Since the groove 218 increases in depth, as it proceeds clockwise from point 212, as the forming roll is rotated with respect to the fixed cam shoe, the walls enclosing the tube at the tangential point of contact will gradually define the enlarged cross section of FIG. 14 permitting the tube to elastically expand in a transverse plane, while, at least in the early stages of bending, being slightly elastically restricted top and bottom by flat diverging walls 230.

It has been noted with respect to groove 200 of cam shoe 186 that this groove is defined uniformly by a radius R drawn from a point 202 (FIG. 15) disposed in the plane of face 198.

Groove 218 of forming roll 40 is defined by a radius R drawn from a point 224 (FIG. 15). The position of point 224 with respect to faces 216, 220 will vary, however, about the periphery of roll 40.

With the forming roll in the position of FIG. 1, groove 218 at point 212, for example, is defined by a radius R, drawn from a point 224 which, though offset by an amount d, from the plane of face 220, nonetheless lies closer to such face than at locations further clockwise from point 212. Point 224 thus more nearly coincides with point 202 than at later bending stages, and the resulting groove cross section is in a form somewhat approximating a circle surrounding tube 170.

As forming roll 40 is located through a small angle alpha (FIG. 9), the point 224 is gradually offset to a greater degree from the plane of face 220 by an amount which eventually becomes d Thereafter, the locus of points 224 is defined at a constant radius V-d from the center 222 throughout the arcuate face portion 220 of the forming roll.

Thus, at point 213 of FIG. 9, the radius R on which the walls defining groove 218 are defined is offset from the face 220 by an amount d In FIG. 15, this offsetting of the radius defining the walls of groove 218 is schematically shown wherein the point 224 from which the radius R is drawn is shown displaced a distance d from face 220 of forming roll 40.

It should be emphasized that the groove 218 defined by a radius R drawn from a point 224 offset from the face of the forming roll is defined gradually through the angle alpha. This results from the fact that the bottom of the groove 218, as viewed in FIG. 9, is flat through that portion thereof falling within the limits of the angle alpha. Thus, throughout the angle alpha the point 224 becomes gradually more offset from the plane of face 220. Thereafter, the groove 218 of face 220 is uniformly defined by walls drawn on a radius R offset a distance d from the face 220.

FIG. 15 is thus intended to reflect schematically the cross secton of the opposed grooves 200, 218 at a position of the arcuate face 220 of the forming roll and cam shoe 186 such as taken along the line 1444 of FIG. 2.

Describing the character of groove 218 in another fashion, it may be said that through the zone of arcuate face 220, the bottom portion 232 (FIG. 9) of groove 218 is drawn on a radius r from center 222 of forming roll 40. The bottom portion 234 (FIG. 9) of groove 218 in the region of flat face 216 does not intersect portion 232 tangentially, but rather is offset radially outwardly from center 222 and from true tangent 236 by an amount d minus d,. Bottom portion 232 is connected to bottom portion 234 by a flat bottom portion 238 defined through the angle alpha, and intersecting bottom portion 234 at an angle B. Obviously, as the locus of points 224 about which radius R, is drawn shifts toward or away from center 2222, the length of sidewalls 230 will increase or decrease thus increasing or decreasing the elastic squeeze exerted on tube 170, top and bottom (FIG. 14).

The purpose of defining a groove of increasing depth in the forming roll is to provide a. slight clearance to permit the tube to elastically deform in a transverse plane as it progresses through the bending operation while confining the tube to a limited degree on the top and bottom. This permits the material of the tube wall to flow transversely within its elastic limit during the bending operation, thus to reduce not only buckling in the tube wall but also ovality" of the tube characteristic of many prior art tube-bending tools.

The amount of depth increase that is provided in the forming roll 40 when the groove 218 is defined therein may vary depending upon many conditions such as the size of the tube being bent, the tube materials, and the degree of bend imparted to the tube. It is not possible to state precisely, therefore, exact numerical values without knowing the precise conditions under which the tube-bending tool is to operate. It can be stated generally, however, that the degree of depth increase is relatively small as compared to the diameter of the tube, being on the order ofa few thousandths of an inch.

It is now known precisely what position the tube takes within the grooves 200, 218 during the bending operation. Tube 170 has been pictured in FIG. 14, however, as lying in a position wherein the center point C of the tube is disposed midway between points 202 and 224 (the points of origin of the respective radii R defining grooves 200, 218). With reference to FIG. 15, it should e remembered that point 202 of FIG. 14 lies within the plane of face 198 of cam shoe 186. Point 224, on the other hand, is offset a given distance from the plane of face 220 of forming roll 40. In the position of FIG. 14, tube 170 is free to expand elastically in two directions as shown by the arrows of FIG. 14. In the schematic representation of FIG. 14 the maximum clearance between the exterior wall of tube 170 and each of the respective groove walls is d /2.

Although not precisely known, it is possible that the tube could assume positions within the grooves 200, 218 other than that shown in FIG. 14. For instance, the tube 170 could be disposed within the grooves in a position such that the center of the tube C coincides with either of the points 202 or 224. If the center C of tube 170 of FIG. 14 should coincide with point 202, the exterior surface of tube 170 will contact the entire groove 200 and a maximum clearance d will be present between the tube exterior surface and the groove 218 thus to permit the tube to expand to the left of FIG. 14. Conversely, should the center C of tube 170 coincide with point 224, maximum clearance will be defined between the tube exterior surface and the groove 200 permitting the tube to expand to the right of fig. 14.

As was previously pointed out, the precise position of the tube 170 with respect to the walls defining grooves 200, 218 is not known and in fact may vary during the tube-bending operation. It is important to bear in mind, however, that the provision of an offset d, as is shown schematically in FIG. 15 permits the tube 170 of FIG. 14 to expand in either or both of the arrow directions during the bending operation.

While in the preferred embodiment of this invention as shown schematically in FIG. 15, the offset ri is defined with respect to the groove 218 of the forming roll, in alternate embodiments of the tube-bending tool of this invention, a slight offset could be provided in the cam shoe. The offset d in the forming roll is preferred, however, since the forming roll rotates with respect to the fixed cam shoe and it is considered desirable to surround the tube with substantially circular groove walls when the tube is initially positioned in the tubebending tool as shown in FIG. 4 and thereafter to gradually impart an offset to the groove in the forming roll as the forming roll is rotated with respect to the cam shoe through an angle alpha.

It will be noted from FIG. 1 that the flat face 216 of forming roll 40 has a significant length. The purpose of flat face 216 is to provide substantial support for the tube in the initial setting up of the tube prior to the bending operation. It will be noted in FIG. 1 that the combined length of flat face 216 and cam shoe 186 is greater than the diameter of the forming roll itself and provides a substantial support for the tube 170 in the tube-bending tool. In addition, the elongated flat face 216 in combination with the tube clamp 156 provides continuous support for the tube during the bending operation.

OPERATION A brief description of the operation of the tube-bending tool of this invention will now be made with reference to FIG. 1.

Assuming it is desired to place a bend in a tube, handle 208 of FIG 1 is first moved in an upward direction in order to unlock or open cam shoe 186 with respect to forming roll 40. Thereafter, crank arm 32 (FIG. 2) is rotated in order to bring the forming roll 40 into the position of FIG. 1. A tube 170 is then positioned in groove 218 of forming roll 40 with the leading edge of the tube being brought past the forming roll until it abuts member 180 with centering tip 182 disposed within the tube end.

Thereafter, tube clamp 156 is rotated from its initial set up position of FIG. 8 to the tube-engaging position of FIG. 7. Clamping is accomplished by pivoting the tube clamp mechanism 156 about the tube clamp bar 154 to the position of FIG. 7 and thereafter rotating locking jaw 168 by means of handle 164 into the position of FIG. 7. Next, handle 208 is moved into engagement with cam shoe 186 thus bringing cam shoe 186 into contact with forming roll 40.

Pointer 62 may now be set to a desired position on the scale 68. Turning of crank arm 32 will produce rotation of forming roll 40, tube clamp bar 154, tube clamp mechanism 156 and abutment plate 56 to produce a bend in the tube. Turning of the crank arm 32 should continue until abutment 56 contacts pointer 62 whereby a desired degree of bend will be placed in the tube. The tube may subsequently be removed from the tube-bending tool by unlocking the cam shoe 186 and disengaging the tube clamp mechanism 156 from the tube.

Indicia are provided on cam shoe 186 for the purposes of assisting the operator in producing a bend with a specified leg. Suppose, for example, that the operator is to place a 60 bend in a tube with a leg of 4 inches from the end of the tube to the bend. With the tube-bending tool of this invention the operafor may produce a bend with a specified leg by simply scribing a line on the straight piece of tubing and aligning that scribed line with a corresponding line on the cam shoe. Where a 4- inch leg on a piece of tubing is desired with a 60 bend, a scribe line is placed on the tube 4 inches from the end of the tube. This scribe line is thereafter positioned opposite the 60 mark on the cam shoe. After the bending operation, the resulting tube will include a 60 bend with a 4-inch leg. Ifa bend is required in the tube with a 5-inch leg, a scribe line is first placed on the tube surface 5 inches from the end of the tube. This scribe line is thereafter positionedl opposite the 90 scribe line on the cam shoe. After turning through 90 the resulting leg will be 5 inches long. Stated another way, the distance from the free end of the bent tube to the bend will be 5 inches.

For ease of description, the principles of the invention have been set forth in connection with but a single illustrated embodiment showing the tube-bending tool. It is not our intention that the illustrated embodiment or the terminology employed in describing itbe limiting inasmuch as variations in these may be made without departing from the spirit of the invention. Rather, we desire to be restricted only by the scope of the appended claims.

We claim:

1. In a tube-bending tool:

a forming roll;

means for turning said forming roll;

tube-supporting mean;

said forming roll having an arcuate side face with a groove defined therein; I

said groove in said forming roll defined in section by an arcuate wall formed on a radius R from a point offset a distance from the plane of said side face;

said distance having a variable length which is a function of the rotation of said forming roll;

said supporting means :having a surface with a groove defined therein;

said groove in said supporting means defined in section by an arcuate wall formed on a radius R from a point in the plane of said surface;

the walls defining said groove of said supporting means and said groove of said forming roll together adapted to support a tube in a transverse plane while providing a space of variable depth for the tube to be deformed during the bending operation. I

2. The invention of claim 1 in which said distance increases from a first length d, to a second length d through a given angle of rotation alpha of said forming roll.

3. The invention of claim 2 in which said distance remains a constant length d, after rotation of said forming roll through an angle alpha.

4. The invention of claim 2 in which the progression from length d, to length d, is linear.

5. The invention of claim in which said forming roll is substantially circular in shape and includes a flat surface extending tangentially from said roll and intersecting said arcuate side face;

said surface of said supporting means being fiat and complementary to said flat surface of said forming roll;

a groove defined in said flat surface of said forming roll, said groove in said forming roll flat surface being defined in section by an arcuate wall formed on a radius R from a point offset a distance d, from said forming roll flat sur- 1 face;

the distance d plus the length of radius R being approximately equal to the length of radius R.

6. The invention of claim 1 in which R, is less than R.

7. The invention of claim 6 in which R is approximately equal to the outside radius of a tube to be received in the tubebending tool.

8. The invention of claim 1 in which the wall defining the groove of said forming roll is joined to said side face of said forming roll by diverging flat walls.

9. In a tube-bending tool:

a forming roll;

means for turning said forming roll;

tube-supporting means adjacent said forming roll;

said forming roll having a side face with a groove defined therein of variable depth;

said supporting means having a surface with a groove defined therein of constant depth;

said grooves of said forming roll and said supporting means being opposed and together defining a tube-receiving recess having a transverse dimension;

said transverse dimension having a variable length which is a function of rotation of said forming roll thereby providing a space of variable depth for a tube to be deformed during a bending operation.

10. in a tube-bending tool:

a forming roll;

means for turning said forming roll;

supporting means for a tube;

said forming roll having an arcuate side face with a groove defined therein;

said supporting means having a surface with a groove defined therein;

said groove of said supporting means being defined in section by a semicircular wall formed on a radius R from a point in the plane ofsaid surface;

said groove of said forming roll being defined in section by an arcuate wall formed on a radius R from a point offset a distance from the plane of said side face;

the radius R being less than the radius R with the radius R being approximately equal to the outside radius of the tube to be received in the tube-bending tool;

the wall defining the groove of said forming roll joined to the side face of said forming roll by means of diverging flat walls.

11. In a tube-bending tool:

a forming roll;

means for turning said forming roll;

supporting means for a tube;

said forming roll having an arcuate side face with a groove defined therein;

said supporting means having a surface with a groove defined therein;

said groove of said supporting means being defined in section by an arcuate wall formed on a radius R where R is approximately equal to the outside radius of a tube to be received in the tube-bending tool;

said groove of said forming roll being defined in section by an arcuate wall formed on a radius R the walls defining the respective grooves of said supporting means and said forming roll being interconnected by diverging flat walls;

the shortest distance between said flat walls being less than 2R whereby a squeezing force will be exerted on a tube during a bending operation.

12. The invention of claim 11 in which R is less than R.

13. The invention of claim 11 in which said arcuate wall of said forming roll is formed on radius R from a point offset a distance from the plane ofsaid side face.

14, The invention of claim ll in which said sidewalls are defined entirely within said forming roll and said groove of said supporting means is semicircular in section. 

1. In a tube-bending tool: a forming roll; means for turning said forming roll; tube-supporting mean; said forming roll having an arcuate side face with a groove defined therein; said groove in said forming roll defined in section by an arcuate wall formed on a radius R2 from a point offset a distance from the plane of said side face; said distance having a variable length which is a function of the rotation of said forming roll; said supporting means having a surface with a groove defined therein; said groove in said supporting means defined in section by an arcuate wall formed on a radius R from a point in the plane of said surface; the walls defining said groove of said supporting means and said groove of said forming roll together adapted to support a tube in a transverse plane while providing a space of variable depth for the tube to be deformed during the bending operation.
 2. The invention of claim 1 in which said distance increases from a first length d1 to a second length d2 through a given angle of rotation alpha of said forming roll.
 3. The invention of claim 2 in which said distance remains a constant length d2 after rotation of said forming roll through an angle alpha.
 4. The invention of claim 2 in which the progression from length d1 to length d2 is linear.
 5. The invention of claim in which said forming roll is substantially circular in shape and includes a flat surface extending tangentially from said roll and intersecting said arcuate side face; said surface of said supporting means being flat and complementary to said flat surface of said forming roll; a groove defined in said flat surface of said forming roll, said groove in said forming roll flat surface being defined in section by an arcuate wall formed on a radius R2 from a point offset a distance d1 from said forming roll flat surface; the distance d1 plus the length of radius R2 being approximately equal to the length of radius R.
 6. The invention of claim 1 in which R2 is less than R.
 7. The invention of claim 6 in which R is approximately equal to the outside radius of a tube to be received in the tube-bending tool.
 8. The invention of claim 1 in which the wall defining the groove of said forming roll is joined to said side face of said forming roll by diverging flat walls.
 9. In a tube-bending tool: a forming roll; means for turning said forming roll; tube-supporting means adjacent said forming roll; said forming roll having a side face with a groove defined therein of variable depth; said supporting means having a surface with a groove defined therein of constant depth; said grooves of said forming roll and said supporting means being opposed and together defining a tube-receiving recess having a transverse dimension; said transverse dimension having a variable length which is a function of rotation of said forming roll thereby providing a space of variable depth for a tube to be deformed during a bending operation.
 10. In a tube-bending tool: a forming roll; means for turning said forming roll; supporting means for a tube; said forming roll having an arcuate side face with a groove defined therein; said supporting means having a surface with a groove defined therein; said groove of said supporting means being defined in section by a semicircular wall formed on a radius R from a point in the plane of said surface; said groove of said forming roll being defined in section by an arcuate wall formed on a radius R2 from a point offset a distance from the plane of said side face; the radius R2 being less than the radius R with the radius R being approximately equal to the outside radius of the tube to be received in the tube-bending tool; the wall defining the groove of said forming roll joined to the side face of said forming roll by means of diverging flat walls.
 11. In a tube-bending tool: a forming roll; means for turning said forming roll; supporting means for a tube; said forming roll having an arcuate side face with a groove defined therein; said supporting means having a surface with a groove defined therein; said groove of said supporting means being defined in section by an arcuate wall formed on a radius R where R is approximately equal to the outside radius of a tube to be received in the tube-bending tool; said groove of said forming roll being defined in section by an arcuate wall formed on a radius R2; the walls defining the respective grooves of said supporting means and said forming roll being interconnected by diverging flat walls; the shortest distance between said flat walls being less than 2R whereby a squeezing force will be exerted on a tube during a bending operation.
 12. The invention of claim 11 in which R2 is less than R.
 13. The invention of claim 11 in which said arcuate wall of said forming roll is formed on radius R2 from a point offset a distance from the plane of said side face.
 14. The invention of claim 11 in which said sidewalls are defined entirely within said forming roll and said groove of said supporting means is semicircular in section. 